Why do we use sodium flouride instead of calcium flouride in our toothpastes, mouthwashes etc? it's much less toxic than sodium flouride.

More effective: Because it's more effective and it is safe when used properly. When examining calcium Fluoride vs. Sodium Fluoride and teeth, in terms of efficient delivery of Fluoride to the teeth, sodium Fluoride is the desired choice because of its solubility. In aqueous solution, sodium Fluoride has a solubility of 18, 000 ppm, while calcium Fluoride only has a solubility of 8 ppm.

Not bio-available: The short answer is that calcium Fluoride is so extremely insoluble as to be considered unusable by your body. Sodium and stannous fluorides are able to be broken down and then the fluorides can enter into and bond with the enamel. Enamel is made of a ring of ions and the Fluoride substitutes in the center to form a more stable ring. This new "ring" is more resistant to decay.

Chemistry of Mouth: Build up on your teeth called tartar or calculus is chemically calcium carbonate (same as limestone). If we used calcium Fluoride in toothpaste, it would increase the amount of build-up on the teeth leading to more periodontal problems and require you to need your teeth cleaned more frequently.